The invention relates to a process for the production of non-woven material from endless filaments which are drawn off from spinnerets in the form of a warp by means of a gaseous propellant and are deposited, after moving through a tube-like filament draw-off device, on a substrate for the formation of the non-woven material. To obtain a desired filament draw-off force, the gaseous propellant is supplied to a filament draw-off nozzle, located at the input side of the filament draw-off device, with a set input pressure (compressed air pressure) and with a set input volume (amount of compressed air), and wherein the warp is spread before being deposited by means of a spreading extruder having Coanda shells adjoining the filament draw-off device, and furthermore, the invention relates to an apparatus for carrying out the process.
Processes and apparatus of the species mentioned above are known from German patent No. 1 785 158, British patent No. 1 282 176 and British patent No. 1 297 582. There a warp coming from a liquefied material and through spinnerets is guided through a filament draw-off device having a filament draw-off nozzle at its upper end fed with highly compressed air.
The so-called Lavalle enlargement adjoins the narrowest annular slit of the filament draw-off nozzle at the exit of which low pressure is generated, which also occurs via a small inner filament-guide at the input side of the filament draw-off nozzle and makes possible the threading of the warp.
A filament offlet with an inner diameter of the Lavalle enlargment adjoins the Lavalle enlargement, into which air flows at supersonic speed. After about half the distance of the filament offlet of a total length of approximately 250 mm a compression shock with following subsonic flow occurs, which further slows inside the adjoining filament guide tube having a four- to six-fold diameter.
Within the filament draw-off device consisting of the filament offlet and the filament guide tube the drawing of the filaments takes place, which thereby become thinner. The substantial part of the filament draw-off force is provided by the filament offlet. The object of the filament guide tube is only to transport the warp to a spreading extruder equipped with Coanda shells and, in order to distribute the filaments and to spread them before they fall or impact on a substrate for the formation of the non-woven material.
The Coanda effect utilized here as well as the Coanda shells mentioned have already been described in detail in German patent No. 1 936 354 and German laid-open publication DE-OS No. 2 200 782 (see FIG. 5b there).
The spreading of the warp by the spreading extruder is of crucial importance for the quality and structure of the non-woven material. The more even the spreading or distribution, the better the quality of the non-woven material.
Although the known spreading extruder with Coanda shells in principle makes possible a spreading of the warp by means of flow techniques, in actuality it could be observed again and again that the eveness of the structure of the non-woven material left something to be desired and that there were limits in regard to the quality of the non-woven material. This was caused by an insufficient spreading or distribution of the warp.
It is the object of the invention to create a process making possible an even spreading or distribution of the warp by means of the spreading extruder in order to increase the quality of the non-woven material. Furthermore, the invention is to provide an apparatus for carrying out the process.